Love interest for John Watson in new Sherlock episode The Sign of Three?

Watson met his wife in the novel the new Sherlock episode is based on (Picture: BBC)

The title of the second episode of Sherlock’s third season will be The Sign of Three, it has been announced, following series opener The Empty Hearse.

The name presumably relates to Arthur Conan Doyle’s Holmes novel The Sign of Four, in which Watson meets his future wife Mary Morstan.

The Sign of Three’s script will come from Steve Thompson, who also penned the much poured-over final episode of series two, The Reichenbach Fall.

It was previously confirmed by Sherlock co-creator Mark Gatiss that the first episode of the new season, set to air later this year, will be called The Empty Hearse (alluding to Sherlock’s faked death).

This instalment will be based on original story The Adventures of the Empty House, which introduced villain Sebastian Moran.

The secret of Sherlock’s faked death will be revealed in series 3 (Picture: BBC)

Gatiss previously said of the episode: ‘There’s certain things about The Adventure of the Empty House which feel set in stone because that’s how Sherlock comes back, but at the same time we feel free to invent and to introduce new stuff to it.’

Show producer Sue Vertue urged fans to keep spoilers under wraps earlier this week, writing in a blog post: ‘ As many of you are aware, we’ll soon be embarking on our first London leg of filming for series 3. I’m also aware that there is quite a lot of speculation about where we’re shooting when. I can’t stress how much we the Producers and Benedict, Martin and the rest of the cast appreciate your love and dedication to our show – we’ll endeavour to live up to your expectations for Series 3.

‘What I am nervous about is that our London shooting schedule is punishing and will really give us very little time to interact with you. The actors really hope you understand that.

‘Also, and I know this is probably asking a lot, the majority of fans and indeed ourselves would REALLY appreciate it if you didn’t post pictures or spoilers or ideally our daily locations.’